Process for hardening layers which contain gelatin within a silver halide photographic material with an aldehyde and an isonitrile

ABSTRACT

A process for hardening layers which contain protein in which the layer is treated with an aldehyde or an aldehyde-donor and with a water soluble, aliphatic or araliphatic isonitrile compound.

United States Patent [191 Ugi et a1. Aug. 26, 1975 [54] PROCESS FOR HARDENING LAYERS [52] US. Cl 96/50 PT; 96/11 1; 260/117; WHICH CONTAIN GELATIN WITHIN A 106/125; 96/51 SILVER HALIDE PHOTOGRAPHIC [51] Int. C1. G03C 5/26; 003C l/3O MATERIAL WITH AN ALDEHYDE AND AN [58] Fl1d of Search 96/111, 50 PT, 50 R, 51; ISONITRILE 260/117; 106/125 [75] Inventors: Ivar Ugi, Gruenwald; Heinrich Seibert; Peter Hoffmann, both of [56] References Cited Leverkusen; Dieter Marquarding, UNITED TE PATENTS Odenthal-G1oebusch; Harald von 2,766,247 ""10/1956 Middleton 96/111 Rintelen; Erwin Ranz, both of 3,295,976 1/ I967 Abbott et a1... 96/111 Leverkusen; Wolfgang 3,554,987 1/1971 Smith 96/1 1 1 Himmelmann, opladen, all of 3,701,664 10/1972 Piller et a1. 96/111 Germany Primary Examiner-W0n H. Louis, Jr. [73] Assigneez Agfa-Gevaert Aktiengesellschaft, Attorney, Agent, or Firm connony and Hutz Leverkusen, Germany [22] Filed: Apr. 10, 1973 57 ABSTRACT [21] App]. N0.: 349,764 A process for hardening layers which contain protein in which the layer is treated with an aldehyde or an 1 Foreign Application Priority Data aldehyde-donor and wlth a water soluble, aliphatic or Apr. 14, 1972 Germany 2218009 araliphatic isonitrile compound.

10 Claims, N0 Drawings PROCESS FOR HARDENING LAYERS WHICH CONTAIN GELATIN WITHIN A SILVER HALIDE PHOTOGRAPHIC MATERIAL WITH AN ALDEHYDE AND AN ISONITRILE This invention relates to a process for hardening layers which contain gelatin, in particular photographic layers.

Many cross-linking agents or hardeners for gelatin have already been described, for example metal salts such as salts of chromium, aluminium or zirconium, aldehydes or their derivatives, in particular formaldehyde, dialdehydes, mucochloric acid, diketones, quinones and chlorides of dibasic organic acids, dianhydrides and in general, compounds which contain several reactive vinyl groups, such as vinyl sulfones and acrylamides. Compounds which contain at least two heterocyclic three membered rings which are easily split, such as ethylene oxide and ethylene imine, may also be used as hardeners for gelatin.

Polyfunctional methanesulfonic acid esters and bisa-chloroacylamido compounds and derivatives of cyanuric acid chloride and dichloroquinoxaline derivatives have also been described.

High molecular weight hardeners such as polyacrolein and its derivatives or copolymers of alginic acid derivatives have also become known in recent times. There are used particularly as diffusion resistant hardeners which are confined to a particular layer.

Many of the known compounds, however. are not suitable for photographic purposes. Some of them are photographically active while others cannot be used because they have such a deleterious effect on the physical properties of the gelatin layers, e.g. their brittleness. Others again tend to discolour or alter the pH during the hardening reaction. Some cross-linking agents for gelatin also damage the skin, e.g. compounds which contain ethylene imine or ethylene oxide, so that they are unsuitable on physiological grounds. Lastly, for hardeners which are to be used for photographic gelatin layers it is very important. both for the purpose of preparing the layers and for processing them, that one should be able to control the cross-linking reaction within certain limits from the very beginning of the reaction, for example by suitable choice of the drying temperature or of the pH. 4

ln many cases it is desirable in practice to use socalled latent hardeners. By latent hardening is meant a cross-linking reaction which is only fully effective after the material has been subjected to a certain treatment, e.g. the action of alkalies or other factors such as heat. Compounds which are predominantly latent in their action are of great practical importance because the photographic material should not undergo any change while it is stored before it is processed. The reason for this is that the maximum densities obtainable, the values and possibly also the light sensitivity of the photographic material decrease with an increasing degree of cross-linking of the layers.

Most of the known hardeners are either too rapid or too slow in their action. If two reactive hardeners are used. eg. cyanuric acid chloride, the viscosity of the casting solution increases even while the solution is being prepared. before it is cast. In certain casting ma- 6g chines, this causes a constant change in the thickness of the layers. lf the hardeners are too slow in their action as is the case. for example. with trisacryloylhexahydrotriazine. the viscosities are not affected and the end points of hardening of the layers are reached only after a prolonged time in storage. All other types of hardeners have properties which are more or less intermediate between those extremes described above.

Processes have already been described in which hardeners which are basically slow in their action are activated by the addition of so-called hardening accelerators. Thus layers which contain trisacryloylhydrotriazine as hardener can be cross-linked spontaneously by coating them with tertiary amines or alkaline solutions. The photographic properties of these layers, however, often leave much to be desired.

It is an object of this invention to find substances for hardening layers which contain protein, in particular, photographic gelatin layers, which enable the layers to be hardened completely within a sufficiently short time and which are photographically inert.

It has now been found that this problem can be solved surprisingly simply by hardening the protein layers with an aldehyde or a compound which splits off aldehyde, in the presence of a water-soluble, aliphatic, cycloaliphatic or araliphatic isonitrile compound.

lsonitrile compounds suitable for the process of the invention correspond to the following formulae:

m an integer of from I to 6,

n 4 or 5.

The following isonitrile compounds have proved to be particularly suitable:

3-lsocyanosulpholan y =COONa(K) Y -COONa(K) under vacuum. The dark brown residue is dissolved in 1000 ml of methylene chloride and 252 g of triethylaminc. and 91 ml olphosgene are introduced into this solution at a temperature ofabout 35C with stirring. Stirring is then continued for 15 minutes ammonia is introduced at l()C until the solution is saturated with ammonia, and the precipitate is then filtered off. The filtrate is concentrated by evaporation under vacuum at a bath temperature of 35C. The residue is filtered over silica gel (benzene/ethyl acetate 1:1 and charcoal (methanol) and recrystallised from methanol.

Yield: 80 g (55% of the theory). m.p. 9494.5C.

C,-,H NO- .S( 145) Calculated: C 41.30; H 4.83; N

9.66; S 22.05; Found: C 41.3; H 4.9; N 9.8; S 21.8

2-lsocyano- 1 -methoxy-ethane 94 g of Z-N-formylamino-l-methoxy-ethane are dissolved in 200 ml of methylene chloride and 200 ml of triethylamine. 100 g of phosgene are then introduced. After stirring for minutes, the solution is saturated with gaseous ammonia at. 10C, the precipitate is suction filtered and thefiltrate is concentrated by evaporation under vacuum (bath'temp'erature C) and the residue is distilled under vacuum. Yield: 29 g (37.5% of the theory) hp. 18 mm 50C..

N.l\l-Bis- 1 3-isocyanopropy1)-piperazine 343 g of N,N-Bis-l-(3-N-formylaminopropyl)- piperazine are dissolved in 1750 ml of methylene chloride and 870 ml of triethylamine. and 272 g of phosgene are introduced at 10 to 15C with vigorous stirring. Stirring is then continued for 10 minutes and the solution is then saturated with gaseous ammonia at 10C. The precipitate is suction filtered and washed thoroughly with methylene chloride. The filtrate is distilled off under vacuum at a bath temperature of 30-35C and the residue is recrystallised from methanol. Yield: 2.30 g (7571 of the theory). m.p. 8081C.

N-Methyl-N-1-( 3-isocyano)-piperazine is prepared.

in analogous manner.

3-lsocyano-1-(N-morpholino)-propane 1316 g of 3-Amino-l(N-morpholino)-propane are introduced dropwise into 1500 g of methyl formate with vigorous stirring and the mixture is then heated to boiling for 10 hours. The volatile constituents are removed under vacuum (water pump) at a bath temperature of 75C. The oily residue is dissolved in 4500 ml of methylene chloride and 2805 ml of triethylamine. and 877 g of phosgene are introduced at C with stirring. The reaction mixture is cooled to 5C and 300 to 350 g of ammonia are introduced. The reaction mixture is then filtered and the filtrate concentrated by evaporation under vacuum (water pump) at 50C. The residue is distilled. Bp 7273C/0.25 mm Hg. yield: 1100 g (82/1 theory) c.H.,N. .o 154) Calculated: c 62.31; H 9.15; N 18.17; 0. 10.38; Found: C 62.6; H 9.6.; N 18.0; 0. 10.5

of the and CN(CH ),,N(CH,,). (n 2. 3)are prepared in analogous manner.

Sodium salt of 'y-isocyanobutyric .acid 1 1 70.0 g of the hydrochloride'of methyl 'y-aminobutyrate were suspended in 280 ml of methylene chloride and then heate'd to boiling after the addition of 250 ml of methyl formate. 49 g of triethylamine are then added dropwise with stirring and after 10 hours the reaction mixture is cooled to 5C. The precipitate is suction filtered and the filtrate is concentrated by evaporation under vacuum at a bath temperature 40C. The residue is dissolved in'250 m1 ofmethylene chloride and 1 10 ml of triethylamine, and 38 g of phosgene are introduced at 3040C with stirring. The reaction is left to continue for 10 minutes and the reaction mixture is then saturated with ammonia at 10C, the precipitate is suction filtered, the filtrate is concentrated by evaporation under vacuum and the residue is distilled under vacuum. 25.4 g of methyl y-isocyanobuty'rate (b.p. 0.35 mm 6775C) are obtained, which are then introduced dropwise into 1 10 ml-of 2N sodium hydroxide solution at 10C with stirring. After leaving the reaction mixture to stand at room temperature for 24 hours, it is concentrated by evaporation under vacuum at a temperature of up to 30C. The solid residue is washed with benzene and recrystallised from methanol. Yield: 26 g (42.571 of the theory), m.p. 156-159C. The sodium salts CN-(CH ),,COOna (n 1.2.4.5,6) are prepared in analogous manner.

Potassium salt of o-isocyano-caproie acid 98 g of the hydrochloride of ethyl 6-aminocaproate are suspended in 300 ml of methylene chloride and covered with a solution ofl06g of soda in 200 m1 of water. A mixture of 75 mol of 98% formic acid and 63 ml of acetic anhydride which has previously been left to stand for one-half hour is introduced dropwise with vigorous stirring. The reaction mixture is left to react for 1 hour and the aqueous phase is then separated off. Concentrated aqueous soda solution is added to the organic phase until the pH is 7.5 to 9 (controlled by pH meter) and the organic phase is cooled to 0 to 5C. g of phosgene are then introduced and at the same time concentrated sodium hydroxide solution is added dropwise to maintain the pH constantly between 7.5 and 9. After 1 hour. ml of water are added and the organic phase is separated off. dried and concentrated by evaporation under vacuum. The residue is distilled under vacuum (b.p. 0.13 mm 71-72C) and intro' duced into 335 ml of ethanol together with 26.6 g of KOH at 10C. This reaction mixture is stirred for 2 hours and evaporated under vacuum at a bath temperature of 2530C. The solid residue is triturated with 330 ml of benzene, suction filtered and dried. Yield: 68 g (72.5% of the theory). m.p. 222C.

The potassium salts CN(CH. ,),,COOK (n 1,234.6) are prepared in analogous manner.

lsocyano acetic acid amide 10 g of ethyl isocyanoacetate [l. Ugi et al. Angew. Chem. 77, 492 1965)] are dissolved in 50 ml of ethanol and the solution is cooled to to C. A catalytic quantity of sodium methoxide is added and ammonia is istroduced for l hour. The clear solution is concentrated by evaporation under vacuum at room temperature and the solid residue is washed with a small quantity of cold propanol and ether and suction filtered. Yield: 5 g (837! of the theory), m.p. l2ll22C.

-y-lsocyanobutyric acid amide 30 g of methyl 'y-isocyanobutyrate are dissolved in 100 ml of methanol, and ammonia is then introduced for one hour without cooling. The temperature rises to about 45C. The reaction mixture is left to stand at room temperature for 3 days and then concentrated by evaporation under vacuum. The residue is recrystallised from ethyl acetate. Yield: l3 g (50% of the theory), m.p. 6465C. C. ,H,,l\l- ,O 1 l2) Calculated: C 53.55; H 7.19; N 24.99;

Found: C 53.7; H 7.4; N 24.6

The compounds CN-(CH. ,),,CONH (n 2,456) and CN(CH- )),,CON(CH,-,). (n l-6) and \CH:CH.

are prepared in analogous manner. V

[X. CNCH CO-NHNH lsocyano-acetic acid hydrazide 10 g of ethyl isocyanoacetate [l. Ugi et al, Angew. Chem. 77, 492 1965)] are dissolved in 40 ml of ethanol. After cooling to 0C, 5 g of hydrazine hydrate are introduced dropwise and the reaction mixture is stirred at 0C for l hour. The crystalline product is then suction filtered and washed with a little cold ethanol and ether. Yield: 7.8 g (8971 of the theory) m.p. 9293C.

The hydrazides Cl\l(CH ),,CO-NHNH (n 2-6) are prepared in analogous manner Sodium salt of l-isocyano-cyclohexane carboxylic acid-( 1 46 g of N-formyl-l-amino-l-carbomethoxycyclohexane are dissolved in 250 ml of ethylene chloride and 83 ml of triethylamine, and g of phosgene are introduced at 40C. The reaction mixture is then stirred for l5 minutes and washed. first with a saturated sodium bicarbonate solution and then with water. The or ganic phase is dried and concentrated by evaporation under vacuum. The residue is distilled (b.p. 0.03 mm 50C) and dissolved in 1 l0 ml of 2N sodium hydroxide solution, the temperature rising to about C. After stirring this solution for 1 hour, it is concentrated by evaporation under vacuum.

Yield: 36.6 g (7771 of the theory), m.p. 320323C (decomposition).

The sodium salt of l-isocyano-cyclopentane carboxylic acid-( I is prepared in analogous manner.

The compounds are prepared from the methyl or ethyl esters COOR (R' -CH C H n 4,5) in analogous manner to the open chain compounds.

The aldehydes or compounds which split off aldehydes used for the process according to the invention may be known compounds commonly used for hardening protein layers, e.g. monoaldehydes such as formaldehyde or aeetaldehyde or dialdehydes such as glyoxal, glyoxal-bisulfite, glyoxal tetraacetate, glyoxal tetracetal, glutaric dialdehyde and suecinic dialdehyde, tria'ldehydes, monoand dimethylolurea and homopolymers and copolymers of acrolein. Aldehydes and compounds which split off aldehydes will hereinafter be briefly referred to as aldehyde compounds.

The process according to the invention is suitable for hardening any protein layers for gelatin foils and in particular photographic layers. By photographic layers are meant layers which are used in photographic materials and especially also light sensitive silver halide-gelatin emulsion layers but also auxiliary layers such as protective layers, filter layers, antihalation layers, backcoating layers, NC layers, etc..

The light sensitive emulsion layers for which the hardening process according to the invention is particularly suitable are. for example. those layers which are based on non-sensitized emulsions, orthochromatic, panchromatic or infra-red emulsions, X-ray emulsions and other emulsions which are not spectrally sensitized. The hardening process according to the invention has also proved suitable for hardening gelatin layers used for various black-and-white photographic processes and colour photographic processes. The process according to the invention has proved particularly advantageous for hardening composite photographic layers used for colour photographic processes, e.g. those which contain emulsion layers with colour couplers or emulsion layers which are designed to be treated with solutions which contain colour couplers.

The aldehydes and isonitrile compounds may also be added at separate stages in the process according to the invention without the effect of the combination being thereby lost. Thus, for example a gelatin layer having a melting point of 50 to 60C (to be defined hereinafter) may be prepared with the addition of isonitrile. and the aldehyde component may subsequently be added to this gelatin layer by bathing the layer in an aqueous solution of the component before the material is processed. The melting point of the layer then increases considerably, and hence also the degree of hardening.

It is also immaterial in principle whether the isonitrile and aldehyde compounds are used together in one layer or in separate layers or whether the second component is poured over the top as an aqueous solution, provided that one of the two compounds is diffusible. The hardening action sets in at once when the two components meet in a layer which consists of a protein or, as in the present case. of gelatin.

The hardening of photographic gelatin layers by the process according to the invention can therefore be achieved either by using the aldehyde and isonitrile compound in the same or different layers of a photographic material or by adding the compounds to preliminary and/or after-hardening baths. With this method. the photographic material may be treated either before or after the photographic process either with separate baths for the aldehyde compounds and for the isonitrile compound or with baths which contain the two compounds together.

According to the invention, the aldehydes are used in quantities of0.l to 8% by weight, based on gelatin, and preferably in quantities of 0.5 to 7% by weight, and the isonitrile compounds are used in quantities of 005 to 1571 by weight and preferably in quantities of 0.1 to 10% by weight.

The usual silver halide emulsions are suitable for the hardening process described here, The silver halide contained in them may be silver chloride, silver bromide or mixtures thereof, optionally with a small silver iodide content, i.c. up to mols percent. Photographic materials prepared with these emulsions may contain the emulsion layers either as single layers, e.g. in the case of simple black-and-white materials, or as several layers arranged above one another, e.g. in the case of colour photographic materials. Each of the individual layers of these layer combinations may contain the usual additives.

The binders used for the photographic layers are protein layers. preferably gelatin although gelatin may be partly replaced by other natural or synthetic binders. Suitable natural binders are e.g. alginic acid and its derivatives such as salts. esters or amides, cellulose derivatives such as carboxymethyl cellulose, alkyl cellulose such as hydroxyethyl cellulose, starch or derivatives of starch such as others or esters or carrageenates. Suitable synthetic binders are: polyvinyl alcohol, partly saponified polyvinyl acetate, polyvinyl pyrrolidone and the like.

The emulsions may also be chemically sensitized, e.g. by the addition ofsulphur compounds during the stage of chemical ripening. for example allyl isothiocyanate, allyl thiourea, sodium thiosulfate, etc.. The chemical sensitizers used may also be reducing agents. e.g. the tin compounds described in Belgian Pat. Nos. 493,464 and 568,687, polyamines such as diethylene triamine or aminomethylsulfinic acid derivatives, e.g. according to Belgian Patv No. 547.323.

Noble metals such as gold, platinum. palladium, iridium, ruthenium or rhodium or compounds of these metals are also suitable chemical sensitizers. This method of chemical sensitization has been described in the article by R. Koslowski, Z. Wiss. Phot. 46, 6572 195 l The emulsions may also be sensitized with polyalkylene oxide derivatives, e.g. with polyethylene oxide having a molecular weight of between l()()() and 20,000, or with condensation products of alkylene oxides and aliphatic alcohols. glycols, cyclic dehydration products of hexitols, alkyl substituted phenyls, aliphatic carboxylic acid, aliphatic amines, aliphatic diamines and amides.

The condensation products have a molecular weight of at least 700 and preferably more than 1000. These sen sitizers may, of course, also be combined to achieve special effects, as described in Belgian Pat. No. 537,278 and in British Pat. No. 727,982.

The emulsions may also be optically sensitized, e.g. with the usual polymethine dyes such as neutrocyanine, basic or acid carbocyanines, rhodacyanines, hemieyanines, styryl dyes, oxonoles and the like. Sensitizers of this kind have been described in the work by F. M. Hammer The Cyanine Dyes and related Compounds, (1964).

The emulsions may contain the usual stabilizers, e.g. homopolar or salt-type compounds of mercury which contain aromatic or heterocyclic rings, such as mercaptotriazoles, simple mercury salts, sulfonium mercury double salts and other mercury compounds. Azaindenes, especially tetraor penta-azaindenes and particularly those which are substituted with hydroxyl or amino groups are also suitable stabilizers. Compounds of this type have been described in the article by Birr, Z. Wiss, Phot. 47, 2-58 1952). Other suitable stabilizers are inter alia heterocyclic mercapto compounds, e.g. phenylmercaptotetrazole, quaternary benzothiazole derivatives, benzotriazole and the like.

The emulsions may also contain the usual additives used for colour photographic materials, e.g. colour couplers.

The activity of the hardener combination according to the invention may be demonstrated in known manner by measuring the melting point of the layers or degree of swelling of the layers.

The melting point of the layers is determined as follows: The layer cast on a support is half dipped into water which is continuously heated to l00C. The temperature at which the layer runs off the support (formation of streaks) is taken as the melting point or melting off point. If no melting occurs at temperatures up to 100C, the layer is again kept at l00C for a maximum of 30 minutes. The measure of the hardening in that case is the length of time after which the layer runs off the support. Under the conditions of measurement, pure gelatin layers without hardener show a melting off point of 30 35C.

Swelling is determined gravimetrically after 10 minutes treatment in distilled water at 22C and is indicated in percent.

EXAMPLE 1 A gelatin-containing silver chlorobromide emulsion which is composed of g of gelatin, 38 g of silver nitrate in the form of the halides and 0.571 of glyoxal (based on the quantity of gelatin) per kg of solution is cast on a layer support of triacetyl cellulose at pH 6.2 and dried. The material is then divided into 3 parts A, B and C. Part B is coated with the following mixture:

500 cc of a 2% aqueous gelatin solution and 4 ml of a 1% solution of compound ll.

Part C is coated with a mixture of 500 ml of a 271 aqueous gelatin solution and 4 ml ofa l 71 solution of compound I in a 1:3 mixture of dimethylformamidelH O.

After drying, the melting points of the samples are determined immediately and after 1 hour, 2 hours and 3 hours storage. The results are summarized in the table below:

Table l The samples are adjusted to pH 6.2 and cast on a layer support of cellulose acetate. The melting points of the layers are determined immediately after drying Sample Melting point after storage of the layers 111 lsmiwmwrh and after 1,234 and 5 hours storage. The following rel 3 3 5 sults are obtained: A 58 5s 5x 5x Table 3 B 62 65 69 74 C 57 72 73 78 Sample Melting points after storage at room temperature with exclusion of moisture in C l 2 3 4 5 hrs. The figures show that the hardening effect of the Q 23 ix 7 combination of aldehyde and isonitrile compound is C D 37 37 37 37 37 37 greater than that of aldehyde alone. E 38 50 56 64 8U 9U EXAMPLE 2 The results show that the isonitrile compounds alone A 3% aqueous gelatin Solution which contains 02% have no hardening effect and that mixtures of formalin of formalin, based on the Weight of gelatin is Cast as an with isonitriles are more powerful hardeners than for- NC layer on a triacetyl cellulose support which has ii alone been prepared on both sides. After drying and 24 hours storage at room temperature with exclusion of mois- EXAMPLE 5 ture. the lay r has 21 m lting point f C. It s then An emulsion layer ofthe following composition is apbathed for 2 minutes in a 1% aqueous solution of complied to a layer support of baryta paper: pound ii and washed f0! 10 minutes. After this (381- 2()() m] of a ilver bromide gelatin emulsion ontainment, the melting point of the layer has risen to 75C. 35 ing 0 EXAMPLE 3 3 /:ltl;Z Wlght ofsilver halide and 671 by weight of gel An aqueous silver chlorobromide emulsion which 4.4 ml of a l()% aqueous solution of saponin. and contains gelatin and is composed of 80 g of gelatin. 40 0.34 ml of a 3071 aqueous solution of formaldehyde. g Of silver nitrate in the form of the halides and 0.471 This is coated with a gelatin solution of the followingof formalin based on the dry weight of gelatin) per kg composition: v of mixture (pH 6.2) is east on a layer support of ethyl- 200 ml of a 2% aqueous gelatin solution, enc terephthalate (Sample A). Half of the mixture cast 4 ml of a 5% solution of Compound "I in a 3:1 mixon the support is covered with a top layer consisting of ture of water/dimethylformamide, and a 2% aqueous solution of compound X (at pH 5.6) 4 ml ofa 10% aqueous solution of saponin. (Sample B). The melting points of the layer were deter- The whole layer contains 2.0 g of silver nitrate per m mined immediately after drying and after 12.3.24 and in the form of silver bromide and 0.07 g of compound hours storage at room temperature. The results "I. h top ayer h ing a hickn f a O t l my. 7 shown in the following table are obtained: 40 After 24 hours storage at room temperature, the

Table 2 Sample Melting points after storage at room Vertical swelltemperature with exclusion of moisture ing after 10 in C minutes washing at 22C 0 l 2 3 24 40 hrs A 62 72 93 95 3957: B l00 100 l00 100 100 3 I07:

As shown in the last column of the table, the addition 50 l y om in ion i no destroy d by keeping it in boilof compound I also reduces the swelling of the layer as g Water for 30 minutes a Whole If the top layer contains formalin instead of compound lll, the resulting melting point is 96C. The top EXAMPLE 4 layer is in that case applied from a casting solution of s the following composition: 100 ml portions of gelatine-containing silver chloro- 2()() f a 27, aqueous gelatin solutionbromide emulsions which contain 100 g of gelatine and 9 i f u 30% aqueous Solution f f ld h d 40 g of silver nitrate in the form of the halides pere kg 4 ml of a 10% aqueous solution of saponin. of emulsion are treated with the following additives:

Sample A: 0.3% of formalin, based on the gelatin EXAMPLE 6 content (in the form of a 1% solution), 60 Sump: 83 0317! of Compound I (in the form of a 1% An isonitrile-containing silver halide emulsion layer solution), of the following composition is applied to a layer sup- Sample C: 0.3% of formalin and 0.3% of compound 1 of hurytu paper:

I (g 200 ml of a silver chloride gelatin emulsion contain- Sample D: 0.37! of compound V (in the form of a 1% solution Sample E: 0.3% of formalin and 0.3% of compound ing 2.5% by weight of silver halide and 7'71 by weight of gelatin, 4.4 ml of a l()/( aqueous solution of saponin and 8 ml of a 5% aqueous solution of compound Vll.

This is coated with a gelatin composition:

200 ml of a 2 aqueous ge 20 ml of a 5 7r aqueous succinic dialdehyde. 4 ml of a aqueous solution of saponin. v The whole layer contains l.5 g of silver nitrate per in in the form of silver chloride pound VII. and the thickness After 24 hours storage at layer combination is not dissolved after. l8 minutes in boiling water.

EXAMPLE 7 A black-and-white photog been only slightly hardened and is not sufficiently resistant for drying on a drying dru with a hath of the following composition after the developed and fixed image has 90 ml of water. 5 ml of compound IV 2.5 ml of a 30% aqueous s A material which is very resistant on the drying drum is obtained in this Way.

solution of the following -Continued Prehardcning hath Melting point of the layer in latin solution.

III B 10' 100C and about 0.6 gv of comof the top layer is about gr tri room temperature. the

raphic paper which has m is treated for 2 minutes been bathed in water:

he layer becomes detached from its support after H) minutes in boiling water.

The figures show that the quantity of formalin used not sufficient on its own to cross-link the gelatin lays so that they become resistant to boiling. A high deee of cross-linking is obtained only when the isoniles are also added.

EXAMPLE 9 The use of the preharden ing bath described in Example 8 is modified as follows.

A slightly hardened layer combination of a colour reversal material prepared in accordance with Fiat Final Report 943, pages 14 and I5, is treated successively with prehardening baths of the following composition.

in olution of formaldehyde.

EXAMPLE 8 Emulsion layers which have not been hardened and which contain 80 g of gelatin and 38 g of silver nitrate 30 in the form of the halides are treated with the following freshly prepared prehardening baths (3 minutes, to

22C) before development: Prehardening bath l 550 ml of water I54 g of sodium sulfate 20 g of sodium acetate 16.6 ml of aqueous so made up to i000 ml with water.

Prehardening bath ll A. 550 ml of water I54 g of sodium sulfate 20 g of sodium acetate 16.6 ml of 3091' aqueous so 5 g of compound I made up to 1000 ml with water B. the same as A. but

10 g of compound I Prehardening bath lll A. 550 m] of water l54 g of sodium sulfate 20 g of sodium acetate 16.6 ml of 30% aqueous so 5 g of compound ll made up to 1000 ml with water B. the same as A.. but

10 g of compound II:

The layers are then washed before determination of the n ing results are obtained:

lrchardcning bath The material is washed for l0 minutes and then dried. After this prehardening process. it was found to lution of formaldehyde to lution of formaldehyde melt off at temperatures above l00C (boiling time more than 10 at 100C).

The same results were obtained with compounds IV.

and VI instead of compound I.

A sample which was treated with Bath A alone was und to have a melting point of 43C.

The same results were obtained when emulsion layers were treated with after-hardening baths by a treatment corresponding to Examples 8 an What we claim is: 1. A process for hardening a photographic material comprising photographically processing a photoaphic material containing on a support a layer containing a protein compound and a silver halide emul- Sit lution of formaldehyde m layer. or a layer ofa silver halide emulsion containing a protein compound wherein the improvement comprises treating the photographic material in a step which contains an aldehyde or an aldehyde-donor compound and an isonitrile compound selected from the group consisting of a watersoluble, isonitrile compound for 10 minutes and dried ielting point. The follow- I Melting point of the layer in II A II B

lll A of the following formula m is an integer of from 1 to 6,

n is 4 or 5.

2. A process as claimed in claim 1 in which before the photographic material is photographically processed said protein-containing layer is successively treated with two prehardening baths, one of which contains said aldehyde compound and the other said isonitrile compound.

3. A process as claimed in claim 1 in which after the photographic material has been photographically processed, the protein-containing layer is treated with an after-hardening bath which contains said aldehyde compound and said isonitrile compound.

4. A process as claimed in claim 1 in which the layer which is to be hardened is of a photographic material and after the material is photographically processed, the layer to be hardened is successively treated with two after-hardening baths, one of which contains said aldehyde compound and the other said isonitrile compound.

5. A process as claimed in claim 1 in which said photographic material consists of a plurality of gelatincontaining layers.

6. A process as claimed in claim 4 in which gelatin is hardened in a multilayered color photographic material; r

7. product according to the process of claim 1.

8. A process as claimed in claim 1 in which the protein -containing layer to be hardened contains one of the treating agents and the other agent is contained in a treatment bath.

9. A process as claimed in claim 1 in which the protein-containing layer to be hardened contains both of said treating agents.

' '10. A process as claimed in claim 1 in which the protein-containing layer to be hardened contains one of the treating agents and the silver halide emulsion layer contains the other treating agent. 

1. A PROCESS HARDENING A PHOTOGRAPHIC MATERIAL COMPRISING PHOTOGRAPHICALLY PROCESSING A PHOTOGRAPHIC MATERIAL, CONTAINING ON A SUPPORT A LAYER CONTAINING A PROTEIN COMPOUND AND A SILVER HALIDE EMULSION LAYER, OR A LAYER OF A SILVER HALIDE EMULSION CONTAINING A PROTEIN COMPOUND WHEREIN THE IMPROVEMENT COMPRISES TREATING THE PHOTOGRAPHIC MATERIAL A STEP WHICH CONTAINS AN ALDEHYDE OR AN ALDEHYDE-DONOR COMPOUND AND AN ISONITRILE COMPOUND SELECTED FROM THE GROUP CONSIST OF A WATERSOLUBLE, ISONITRILE COMPOUND OF THE FOLLOWING FORMULA
 2. A process as claimed in claim 1 in which before the photographic material is photographically processed said protein-containing layer is successively treated with two prehardening baths, one of which contains said aldehyde compound and the other said isonitrile compound.
 3. A process as claimed in claim 1 in which after the photographic material has been photographically processed, the protein-containing layer is treated with an after-hardening bath which contains said aldehyde compound and said isonitrile compound.
 4. A process as claimed in claim 1 in which the layer which is to be hardened is of a photographic material and after the material is photographically processed, the layer to be hardened is successively treated with two after-hardening baths, one of which contains said aldehyde compound and the other said isonitrile compound.
 5. A process as claimed in claim 1 in which said photographic material consists of a plurality of gelatin-containing layers.
 6. A process as claimed in claim 4 in which gelatin is hardened in a multilayered color photographic material.
 7. A product according to the process of claim
 1. 8. A process as claimed in claim 1 in which the protein-containing layer to be hardened contains one of the treating agents and the other agent is contained in a treatment bath.
 9. A process as claimed in claim 1 in which the protein-containing layer to be hardened contains both of said treating agents.
 10. A process as claimed in claim 1 in which the protein-containing layer to be hardened contains one of the treating agents and the silver halide emulsion layer contains the other treating agent. 